In remote control processing systems today, there exists a critical need to monitor dynamically changing host screen activity and transmit screen changes to a remote system. Generally, host-based systems include a main processor which is coupled to a controller unit by a channel. The controller typically has a plurality of terminals coupled thereto. When the main processor wants to display data on display units associated with the plurality of terminals, a block of display data is forwarded over the channel to the controller unit. The controller unit distributes the data to the respective terminal or terminals. In order to improve the efficiency of the transmission of display data between the main processor and the respective terminals, the data is packed by the main processor to maximize the bandwidth of the channel. Moreover, the main processor performs partial updates of the displays associated with the plurality of terminals. In this manner, the main processor transmits to the controller unit of the terminal or terminals requiring display unit updates, the location on the display unit where the update is to take place and the display data needed for the partial update. Using this technique, if only a portion of a screen changes, only that portion which changed is updated while the remainder of the screen remains unchanged.
In personal computer-based systems, each personal computer includes a screen buffer which can be directly written to by a BIOS program associated with the respective personal computer or an application program being executed on the computer. Presently, in personal computer-based systems, there is no way of knowing what has been written to the screen buffer by the application program. Unlike the host-based system, the personal computer-based system does not include a controller which collects the display data used to update the terminals coupled thereto. Moreover, in the host-based system, the main processor does not write directly to the respective screen buffers associated with the plurality of terminals coupled to the controller. Generally, it is not unusual for the personal computer-based system to use a communication link to interconnect a plurality of computers therein. The problem of updating display units associated with the computers in the system becomes acute when the communication link is a slow telecommunication line and the display of a host computer being monitored is changing dynamically.
Consequently, there is a need for a technique for monitoring dynamically changing host computer screen activity and transmitting the screen updates to a remote system using a slow communication medium in a concise manner. Moreover, there is a need for a technique for monitoring dynamically changing host computer screen activity and transmitting the screen updates to a remote system whereby applications write directly to a screen buffer associated with the host computer.